Random 1 block lava sources embedded in Nether

I was building in the nether and kept finding random lava sources embedded in the nether, they killed me many times so I had to investigate. I installed an xray mod to see if these lava sources were a one off thing... but they are everywhere. The Nether of the world was generated in 13w07a.

If this an intended feature to make the Nether more dangerous, I feel it is very unfair combined the flow speed of lava in the Nether.